This issue of CiSE is based on work presented at the US National Science Foundation workshop, Path to Petascale: Adapting Geo/Chem/Astro Applications for Accelerators and Accelerator Clusters, held at the US National Center for Supercomputing Applications (NCSA) in early 2009. The workshop was designed to raise awareness about the emergence of accelerator-based high-performance computing (HPC) resources among computational scientists from the geosciences, computational chemistry, and astronomy and astrophysics communities and to help them get started in using these resources.